1. Field of the Invention
The present invention relates to a starter for an internal combustion engine for starting the internal combustion engine by means of a hydraulic actuator.
2. Description of the Prior Art
A conventional starter of the type mentioned above is known, for example, from Laid-open Japanese Utility Model Registration Application No. 59-73579. This starter has an electric motor and a hydraulic motor such that an internal combustion engine (hereinafter simply called the xe2x80x9cenginexe2x80x9d) can be started by means of either the electric motor or the hydraulic motor. The electric motor has a pinion spline-connected to its rotating shaft. Upon starting the engine, the pinion is axially slid by a plunge mechanism and meshed with a ring gear integrally formed on a crank shaft of the engine.
On the other hand, the hydraulic motor is disposed on the opposite side to the pinion with respect to the rotating shaft of the electric motor, and is coupled to the rotating shaft through a coaxial one-way clutch. The hydraulic motor is driven by an oil pressure accumulated in an accumulator, and controlled to start and stop by opening and closing an electromagnetic ON/OFF valve disposed between the accumulator and the hydraulic motor. The oil pressure is accumulated in the accumulator by a hydraulic pump directly coupled to the engine, where the accumulation of oil pressure is performed and stopped by opening and closing an electromagnetic valve disposed between the hydraulic pump and the accumulator. Also, the accumulation of oil pressure is performed under the condition that the oil pressure within the accumulator is equal to or lower than a predetermined value, and the vehicle is decelerating (the brake is trodden while the vehicle is running), i.e., utilizing regeneration energy.
Upon starting the engine, in this starter, the pinion of the electric motor is meshed with the ring gear by means of the plunge mechanism, and the hydraulic motor is driven when the oil pressure in the accumulator is equal to or higher than the predetermined value. In this manner, the rotation of the hydraulic motor is transmitted to the rotating shaft of the electric motor through the one-way clutch, and further from the pinion to the ring gear to start the engine. On the other hand, when the oil pressure in the accumulator is lower than the predetermined value, the hydraulic motor is stopped, and the electric motor is driven instead to start the engine.
As described above, the conventional starter uses the electric motor for starting the engine when the oil pressure in the accumulator is lower than the predetermined value. The electric motor, however, is disadvantageous in a longer time taken to start the engine, poor startability, and associated noise caused by the meshing of the pinion with the gear ring for a long time, due to its general characteristics of smaller output torque, as compared with the hydraulic motor, which results in a delay in establishing the rotation. Particularly, if the so-called idling stop, recently regarded as important as countermeasures to the environmental pollution and fuel economy, is applied, the foregoing disadvantages are more likely to appear prominently since the engine frequently repeats start and stop during traffic jam and the like. In this regard, since the starter accumulates the oil pressure by utilizing the regeneration energy during deceleration of the vehicle when the oil pressure in the accumulator is lower than the predetermined value, the oil pressure in the accumulator tends to be insufficient during traffic jam and the like, resulting in a failure in utilizing the hydraulic motor. For this reason, the electric motor is frequently used to start the engine, causing the aforementioned disadvantages to appear prominent.
The present invention has been made in view of the problem mentioned above, and it is an object of the invention to provide a starter for an internal combustion engine which is capable of improving the startability and reducing noise associated with starting by maintaining a hydraulic actuator in a usable state irrespective of an operating condition of the internal combustion engine to reduce a starting time.
To achieve the above object, the present invention provides a starter for an internal combustion engine. The starter includes an electric motor, pumping means driven by the electric motor, an accumulator for accumulating an oil pressure pumped by the pumping means, a hydraulic actuator driven by the oil pressure accumulated in the accumulator, an oil pressure supply control valve for controlling the oil pressure supplied from the accumulator to the hydraulic actuator, a driven gear for rotation integral with a crank shaft of the internal combustion engine, a driving gear connected to the hydraulic actuator, and brought into mesh with the driven gear and driven by the hydraulic actuator when the internal combustion engine is started, oil pressure detecting means for detecting the oil pressure in the accumulator, and control means for controlling the electric motor based on the value of the oil pressure in the accumulator detected by the oil pressure detecting means.
According to the foregoing starter for an internal combustion engine, when the internal combustion engine is started, the driving gear is brought into mesh with the driven gear integrally formed on the crank shaft of the internal combustion engine, while the hydraulic actuator is driven by an oil pressure accumulated in the accumulator to rotate, and the rotation is transmitted to the driven gear through the driving gear to start the internal combustion engine. The oil pressure is accumulated in the accumulator by driving the pumping means such as an oil pump connected thereto by the electric motor. In addition, the oil pressure in the accumulator is detected by the oil pressure detecting means, so that the control means controls the operation of the electric motor based on the detected value of the oil pressure.
In the foregoing manner, the oil pressure in the accumulator is monitored at all times to control the operation of the electric motor based on the monitored oil pressure value, so that the oil pressure in the accumulator can be maintained at a level suitable for actuating the hydraulic actuator irrespective of the operating condition of the internal combustion engine. As a result, the internal combustion engine can be started at all times by utilizing the hydraulic actuator which provides a large output torque, even during traffic jam, when the idling stop is applied. Thus, by virtue of the resulting reduction in starting time provided by the rapidly established rotation of the internal combustion engine, it possible to improve the startability and reduce noise associated with the starting.
Preferably, in the starter for an internal combustion engine described above, the control means drives the electric motor when the value of the oil pressure in the accumulator detected by the oil pressure detecting means is equal to or lower than a predetermined value.
In this preferred configuration, the electric motor is driven to actuate the pumping means to increase the oil pressure in the accumulator when the oil pressure in the accumulator is reduced to the predetermined value or lower, so that a sufficient oil pressure can be ensured in the accumulator for driving the hydraulic actuator irrespective of the operating condition of the internal combustion engine. As a result, the aforementioned effects of the present invention can be reliably produced.
Also preferably, the starter for an internal combustion engine described above further includes power switching means for switching the transmission of power of the electric motor to the pumping means or to the driving gear.
In this preferred configuration, the power switching means acts to transmit the power of the electric motor to the pumping means, which is driven thereby, to accumulate the oil pressure in the accumulator as well as to transmit the power of the electric motor to the driving gear, which is driven thereby, to start the internal combustion engine. When the internal combustion engine is, for example, at an extremely low temperature, the electric motor will take a long time until its rotation is established due to its large friction in the starting of the internal combustion engine by the electric motor. On the other hand, the hydraulic actuator is required to ensure stable starting of the internal combustion engine because the hydraulic actuator can structurally provide a torque in a relatively short time. In such a case, according to the present invention, the electric motor for accumulating the oil pressure can be used additionally for starting the internal combustion engine, thereby making it possible to reduce the size and cost of the starter.
Also preferably, the starter for an internal combustion engine further includes oil pressure accumulating means for driving the hydraulic actuator to rotate in a direction reverse to a direction in which the hydraulic actuator is rotated when the internal combustion engine is started to accumulate the oil pressure pumped by the hydraulic actuator with power of the electric motor in the accumulator.
In this preferred configuration, the oil pressure pumped by the hydraulic actuator with the power of the electric motor is accumulated in the accumulator by the oil pressure accumulating means. In other words, since the hydraulic actuator additionally functions as the pumping means, the oil pump is eliminated, thereby making it possible to further promote the reduction in the size and cost of the starter.